3) Setup an elastic IP, and then create DNS entries for your mail server, that point to that IP. Let’s assume you are going to call your mail server mail1.example.com, you will need records in example.com’s zone for:

1) Launch a new instance. Replace paul-public-key with the name of your public key (this will need to have been imported into AWS previously). The -g switch refers to your security group. We are using 100GB as the main disk size, as by default they are too small for a Zimbra installation.

IMPORTANT: The commands above specify 127.0.0.1 as the IP for the system’s hostname in /etc/hosts. You need all 3 fields listed in /etc/hosts (eg. 127.0.0.1 mail1.example.com mail1) – otherwise LDAP install fails as it tries to connect to resolved elastic IP. In addition, use a CNAME for the public DNS MX records hostname instead of A record, then when it is resolved internally, it should get a local IP, which should assist postfix with LMTP lookups. If you don’t do this you will get issues – http://wiki.zimbra.com/wiki/Incoming_Mail_Problems – A crude fix is to open port 7025 in the security group, but the CNAME is better.
4) Download Zimbra